On Friday, March 7, 2014 6:30:41 PM UTC-6, Martin Gregorie wrote:
IOW, if the IAS in flight shown by a freshly calibrated ASI is not the same
as independently measured TAS then the error is due to the placement of the
static vent and/or the pitot.

This is true only at sea level, standard day conditions in the airspeed range we are interested in. At 5000 feet, IAS and TAS are NOT the same.

For example, its well known that pressure under the wing is above bulk
atmospheric pressure, so a static vent anywhere near the underside of the
wing will make the ASI read low.

Disagree with this. Look at the airspeed corrections on a Schempp-Hirth sailplane using the underwing statics. The Ventus A that Dick Johnson tested is a good example. Goes from reading 4 knots too slow at low speed to 10 knots to fast at high speed.

If you are curioius about the calibration of your indicator, the following should be of interest to you:

http://www.rst-engr.com/rst/articles/KP89JUL.pdf

Steve Leonard